netfilter: ctnetlink: fix sleep in read-side lock section

Fix allocation with GFP_KERNEL in ctnetlink_create_conntrack() under
read-side lock sections.

This problem was introduced in 2.6.25.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/nf_conntrack_netlink.c

@@ -1139,7 +1139,7 @@ ctnetlink_create_conntrack(struct nlattr *cda[],
 	rcu_read_lock();
 	helper = __nf_ct_helper_find(rtuple);
 	if (helper) {
-		help = nf_ct_helper_ext_add(ct, GFP_KERNEL);
+		help = nf_ct_helper_ext_add(ct, GFP_ATOMIC);
 		if (help == NULL) {
 			rcu_read_unlock();
 			err = -ENOMEM;